Dual passage muffler



DUAL PASSAGE MUFFLER Filed Nov. 4, 1955 United States Patent O Thisapplication relates to a method forrmutlling noises produced as forexample by the exhausts of engines,and to novel mullers for practicingtheksame. More particularly, it provid-es a method and mulers whicheffectively muflle such exhausts simply, inexpensively, and withsubstantially no interference with free ow of exhaust gases to theatmosphere. 4

In mufllers heretofore known and used, reliance has been placed onpassing such exhaust gases through a tortuous arrangement of chambersand passages, or through A a chamber lled with some loosely packed sounddeadening material such as glass wool. Such mufllers have beencharacterized by frictional resistance to the passage of gasestherethrough with resulting back pressures and decrease of engineefficiency. j n

I have discovered that surprisingly good muflling may be obtained bygiving to separate streams of free-flowing exhaust gases dillerent soundwave characteristics such that, when said streams are discharged atadjacent outlets, substantial sound wave cancellation thereupon results,giving a surprisingly quiet exhaust. I have found that particularly goodmuflling occurs if exhaust gases are discharged through a mufllercomprising a chamber having emerging therefrom, for passage of gases tothe atmosphere, two conduits with their discharge ends next to eachother and having cross-sectional areas large relative to thecross-sectional area of the chamber.

One advantage of my new method and mufller is that it offers very littlefriction to the exhaust gases passing through it, and thus greatly cutsdown engine back pressure, and correspondingly increases engineeiciency.

A further advantage of the muiller of my invention is its simplicity anddurability of construction. It may be inexpensively constructed ofmaterials having a longer life than the average car.

As an additional feature of my new muiller there preferably is a smallbaflle extending from one side of the abovereferred to chamber a shortdistance interiorly thereof. An advantage of said baille is that duringinitial starting and warm-up of the engine improved muflling effects areproduced thereby.

Other advantages and features of my invention will be apparent from thefollowing description of a preferred embodiment thereof, shown in theattached drawings, in which:

Fig. l shows :a side elevation, partially in section;

Fig. 2 is a sectional view on lines 2-2 of Fig. l; and

Pig. 3 is a section View on hues 3-3 of Fig. 1.

Referring now to the drawings, there is shown in Fig. l an engineexhaust pipe 2 (broken away). Connected to the exhaust end thereof is apreferred embodiment of my new muiller, indicated generally at 4.

I show and describe an embodiment which has operated with completesatisfaction as the mul-ller for a small automobile of the characterpopularly referred to as a Jeep." There is provided a fourteen inchlength of ll/z" iron pipe 6. Extending two inches from the inlet 8 ofsaid pipe 6 is a chamber 10, into which a baille 12 extends from theinner wall of said pipe a short distance interiorly thereof. Said baillemay suitably be a piece of sheet metal inserted in a force t through aslit provided therefor in the wall of the pipe 6.

Extending from s-aid chamber 10 to the outlet end 13 of the pipe 6 aretwo tubes 14 in side-by-side relation. In the embodiment shown, saidtubes are 3A" copper tubing, flattened somewhat to permit forcedintroduction in the pipe 6 Said tubes thus have the same cross-sectionalarea, said area being substantial with respect to the crosssectionalarea of the chamber 10. Said tubes are l2 inches in length, and in theembodiment shown are secured further in the pipe 6 by means of retort-cement 16, which also forms in effect a washer that serves to seal theannular space between pipe 6 and tubes 14 against passage of gastherethrough. The outlet, or discharge, ends 15 of said tubes terminateadjacent to each other and adjacent to the outletendy 13 of the pipe 6.

The exhaust pipe 2 may of course be connected to the muler 4 by anysuitable means, as by a split, offset ring 18 secured toexhaust pipe 2and mufller 4 by clamp rings 20 and 22 respectively.

.In operation, exhaust gases, as from an engine, enter chamber 10,through exhaust pipe 2. Said gases then pass through tubes 14 to theatmosphere, exhaust noise being most satisfactorily muffled. A free andunobstructed path is thus provided for flow of the gas, so that backpressures with consequent lowered engine efficiency are practicallyeliminated. The baille 12, I have discovered, makes for still moreeffective muflling, particularly during engine starting andwarmingjup.`The baille, while preferred, is not essential and may be omitted.

In my new method and muffler, sound waves coming from one pipe interactwith sound waves coming from another so that the fundamental tones arealmost completely canceled out and neutralized. I have observed that ifthe outlet of either of the adjacent tubes 14 is experimentally sealedoff, the gases emerge from the single tube left open with sounds like afiring shotgun. When both tubes are free, however, as in actualoperation, there is simply a low bubbling sound at lower engine speeds,and a buzz at higher engine speeds. When two tubes or conduits of thesame length and cross-sectional area are used, said area being largerelative to the cross-sectional area of the chamber 4, it may be thatoscillation of the gases in the chamber is what causes the tubes tosound in opposite phases, thus resulting in cancellation between thesound waves emerging from the conduits adjacent each other.

I have found that with two tubes of diameter large with respect to thediameter of the chamber, such for example that said chamber is not largeenough to accommodate a third tube of the same size, a much betterresult is achieved than by using more than two tubes of smallerdiameter. I have also found it preferable, though not essential, to useconduits having a free space therearound.

I have also been able to achieve satisfactory results using two tubes ofcertain different lengths (for example, two 3%: inch tubes, one longerthan the other); and in other cases, using two tubes of particulardifferent diameters (for example, 1/2 inch and c/4 inch). In thesecases, apparently, the diiferences between the tubes used produce -orcontribute to producing differences in phase resulting in the desiredcanceling-out effect.

I have been able to achieve satisfactory results using, instead of twotubes, a divider separating the pipe 6 into two compartments (half-moonshaped in cross-section) between the chamber and the outlet end of thepipe, to form a pair of conduits of the same cross-sectional area andlength.

I have also found that the exhaust pipe itself may suitavbly serve asthe chamber, if two conduits of cross-sectional area large with respectto the area thereof are led therefrom, apparently producing witheiiiciency suitable differences in phase in the sound waves emergingfrom the two conduits.

It is preferable, though not necessary, to enclose the conduits ina pipeas in the preferred embodiment. The muller works satisfactorily if thetwo conduits are simply joined to the chamber in air-tight manner andextend therefrom without enclosure of any kind.

It .will be apparent that I have provided the art with a newandeliicient mui-ller which combines the virtues of lower cost and greaterdurability with the advantage of increased engine eiciency, owing tothere being no substantial production of back pressures.

It will also be apparent that modifications within thc spirit of theinvention and the scope of the appended claims will readily occur tothose skilled in the art. And of course muiller dimensions may be variedfor use in connection with engines of dierent sizes.

I claim:

l. A muffler for quiet discharge of exhaust gases without substantialproduction of back pressure which includes a pipe and, mounted therein,two tubes, a baie, and a `sealing washer, said tubes having the inletends thereof spaced from the inlet end of said pipe to form a chamberwithin said pipe, said tubes being of the same cross-sectional area,said area being substantial with respect to the cross-sectional area ofsaid pipe, and said tubes being of the same length and having the outletends thereof adjacent to each other and to the outlet end of said pipe,said washer being positioned around said tubes and within said pipe toprevent passage of gas therebetween, and said balie extending from theinner wall of said pipe generally radially a short distance into saidchamber.

2. A muffler for quiet discharge of exhaust gases without substantialproduction of back pressure which includes -a pipe and, mounted therein,two tubes and a bale, said tubes having the inlet ends thereof spacedfrom the inlet end of said pipe to form a chamber within said pipe, saidtubes being of cross-section area substantial with respect to thecross-sectional area of said pipe, said tubes having the outlet endsthereof adjacent to each other, and said baille extending from the innerwall of said pipe generally radially a short distance into said chamber.

3. A muler for quiet discharge of exhaust gases without substantialproduction of back pressure which comprises a conduit for acceptingexhaust gas from an engine and a pair of tubes of smaller diameter thansaid conduit and connected therewith to lead gases therefrom, said tubeseach being of the same diameter and length, irnperforate, low-friction,and substantially free of absorptiveness or curves that would cause anysubstantial energy loss in a stream of exhaust gas passing therethrough,said tubes terminating in an adjacent side-byside relation with a pairof orices adapted to discharge exhaust gas freely in the atmosphere ingenerally parallel correspondingly directed streams.

4. The muflier of claim 3 in which said tubes have cross sectional areaslarge relative to the cross sectional area of said conduit.

5. A muffler for quiet discharge of exhaust gases without substantialproduction of back pressure which includes a pipe and, mounted therein,two tubes, said tubes having the inlet ends thereof spaced from theinlet end of said pipe to form a chamber within said pipe, said tubesbeing of cross sectional area substantial with respect to the crosssectional area of said pipe and having the outlet ends thereof adjacentto each other.

References Cited in the tile of this patent UNITED STATES PATENTS702,031 Ronan June 10, 1902 1,038,931 Michaelson Sept. 17, 19121,351,122 Paulson Aug. 31, 1920 1,591,088 Holmes July 6, 1926 1,821,688Bourne Sept. 1, 1931 FOREIGN PATENTS 178,815 Germany Nov. 23, 1906428,695 Germany May 10, 1926 116,512 Austria Feb. 25, 1930

